Keying system



Jan. 2, 1940. c. w; HANSELL KEYING SYSTEM I Filed oct. 9, 1937 ATTO R N EY UNITED STAT Patented Jan. 1940 1 AKarma SYSTEM Clarence W. Hansell, Port Jefferson, N. Y., as# signor to Radio Oorporation of America. a

corporation o! Delaware Application October 9, 1937, Serial N0. 168,111

s Claims. (c1. rvs-ss) In describing this invention which concernsl spaces. At present in some cases provision is keying systems vfor highdrequency transmitters, made for adjusting the weight of keying to. reference will be made to the attached drawing some extent by means of volume control in wherein the two figures illustrate automatic vacuum tube keyers and by means of relay ad- I 5 keying means, yincluding means for regulating justments. However, as the art develops toward 8 the heaviness of keying, in combination with a more nearly 100% electrical and vacuum tube tripping circuit or locking circuit which supplies devices keying speeds increase and performance keyed tone impulses of controllable character t0 requirements become more rigid. Seme definite a transxx'ritter. The arrangements of Figures 1 electrical method must be` made available by and 2 are similar in principle. In Figure 1, the means ofI which equal time intervals may be sub- 10 coupling between the keying weight regulating tracted from dots and dashes and added to the means and the tripping circuit is resistive wherespaces. lThis provision 4should be made for all as a/ transformer coupling is usedff at this lpoint services employing keying of direct or alternatin Figure 2. The positioning of the keying weight ing signalling currents, such as ordinary teleregulating elements is somewhat different in graph, time division multiplex telegraph, fac-'l5v each ligure.

simile, etc. In telegraph service one method for In the operation of. high frequency telegraph v Carrying out the marking time subtractionl idea transmitters for long distance service multi-path discussed above while still retaining positive offtransmission causes several rays of transmitted keying vWithout amplitude. dribbling iS t0 take radiation to reach the receiver with different the reversing direct current signalfrom the auto- 20 over-lapplngjarrival times. The effect at the' rematic keying heads or auto heads and apply the ceiver is to increase the marking periods and said reversible impulses to a tripping circuit of decrease the spacing periods so that they are not the Finch type, described in United States Pat-v reproduced in correct proportion at the receivents #1,948,103 and #1,844,950, through a. special ing end. The result is frequently a pronounced time biasing circuit. Such BS SiN-WV in Figures 25- decrease in vreadability of' the received signals,

particularly at' high keying speeds. A similar 1 and 2 of thel drawing.

In the arrangement of Figure 1 an automatic effect occurs in the operation ofcarrfer telegraph transmitter mechanism shown diagrammatically wire line circuits where reflections at various places along the line, and in-illters or other cirample by au automatic typewriter mechanism. 01' $0' at 2, actuated in any manner such as for excuits, frequently cause elongations or the carrier. a perforated paper` tape, not shown, applies recurrent pulses.

verse current pulses to a condenser C1 through This source oi' signal distortiom to a ve'ry large a current limiting and antisparking resistor R1.

extent, has been overcome by means of the key- .The automatictransmitting or keying means ing system disclosed in my United states Patent may be of any type. For example. take transall #1,808,220 wherein the keying circuitswere so mitters as illustrated ln'Mathes United States arranged that the time of travel of an electro- Patent #1,979,484 or Callahan et Val.s United mechanical relay armature was subtracted from `States Patent #2,010,505, or keying means as in the marking time. In commercial practice the Callahans United States Patent #2,086f351 or relay was adjusted so that'the'time of its travel typewriter mechanism as shown in Bradys 40 was approximately equal to the signal elongation United States Reissue Patent #16,485 and Patcaused .by multi-path transmLssion. With this ent #1,523,337. 'In practice, the reverse current arrangement there were practicallyA no compulses may be obtained from. plus and minus plaints o heavy keying from the receiving end power sources at to 150 volts through short of the circ t but under similar'conditions prior circuit protective resistances which are low in 45 to the use o my said system, when transmitters Value compared with other resistances in the keywere keyed perfectly to give equal dots and Spaces ing circuits. The condenser C1 serves as a charge complaints of heavyf keying were frequent and accumulator. to permit operation of thekeying sometimes bitter.'

system following the regulator even when the In order to overcome the above dimcultes protransmitter mechanism shown diagrammatically 50 vision should be made in all keying circuits and atv 2 supplies only short momentary contacts. in particular in keyin'gfcircuits for short-wave The charge built up in condenser C1 of a polartransmitters used over long distances to subtract ity determined by the last contact made by the a deilnite and controllable amount of time from transmitter mechanism 2 passes through resistor each dot and dash and- `add this time to the lRz and (if ofproper polarity) through the rec- 55 tier 6 in parallel with R2 l to condenser C2. 'I'he rectier 6 being a unilateral device passes a. substantial current only in the event the impulse applied to R1 and C1 is negative so that current flows through 6. In the event the last contact is positive current cannot pass through 6 in material amounts and reaches C2] only through R2. Thus, the rate of charging of condenser Cz is greater for impulses of negative polarity than it is for impulses of positive polarity because of the action of the rectifier 6. I'his time difference is substantially proportional to the diierence in time constant of the resistor condenser circuit for the two directions of current ow and is also substantially independentof the keying speed. In practice, the charge carried over to condenser 'C2 has an opportunity to reach a steady state value, or nearly a steady state value, for each pulse of current delivered to the condenser for all keying speeds up to the maximumwhich can be used safely over the long distance wireA or radio circuit with which 4the keyer may be associated. The time constants of the resistance condenser circuit is adjustable in accordance with ordinary operating requirements at R2 and appropriate values of yR1, C1, C2 and R2 are chosen so that the impulses representative of dots and dashes may be made lighter or foreshortened to suit the needsof the particular transmission used. In the particular application the marking impulses, i. c., dots and dashes, are thereby shortened or made lighter an amount suiiicient to subtract from the keying impulses an amount of time equal to that added to the keyed impulses at the receiver by multi-path. transmission.

The keying impulses as regulated are supplied through a resistance I to a tripping and locking circuit of the Finch type shown in generar at 8.

l This tripping and locking circuit comprises an electron discharge tube I2 having its control grid I4 connected to I0 and its cathode grounded, being thereby connected to the common point of the regulating circuit. The anode I6 of vI2 is connected to the grid I8 of tube 20, the anode 22 of the latter tube being connected back to the grid I4 of tube I2. A change of potential in one direction on grid I4 amplified in. I2 acts on I8 to produce a corresponding change in potential atv22 which is fed back to the grid I'4 of Y I2 to produce a blocking or tripping action in the tube. This operation has been described in greater detail in Finchs United States Patents #1,844,950 and #1,948,103.A Thus, positive and negative impulses on the grid of I4 produce positive reversing of -current in the anode circuit of 20 and this reversing of current produces in the potentiometer 24, gridV biasing potentials, or blocking potentials, for the grids of the tubes in unit 30, the input of which is connected to a tone source and the output of which is connected to a line for transmission to a distant point. The line may extend to the receiving point in which case my signal correcting circuit will compensate for signal elongation' due to the eifect of line reilections, lter sections, etc., or it may extend toa radio transmitterv through which connection is made to a. distant receiver in which case my circuit may be used to correct elongations in both wire and radio circuits.v N

Various modifications may be made in thr circuits without destroying the results I wish to obtain. For example, resistance R2 may have substituted therefore an inductance, or a combination of resistance and inductance. The polarity of output may be reversed by connecting the potentiometer 24 to the anode I6 instead of to anode 22V. Likewise the polarity ofthe time biasing may be reversed by reversing the polarity of the rectier 6 or by reversing the polarities of currents supplied to the transmitter mechanism 2 and at the same time moving the potentiometer 24 from anode 22 to anode I6.`

In the arrangement of Figure 2 an automatic reverse current transmitter mechanism 2 supplies currents to charge the condenser C1 positively and negatively in accordance with the telegraph, printer, or facsimile signals which are to be transmitted. Current from the condenser C1 passes through a resistance R3 to a condenser Cs through the parallel combination of -an adjustable resistance R4 and a rectier 6. In parallel with the combination of `condenser C3', resistance R4 and the rectifier 6, as shown, is the primary P of a transformer 40. The transformer has two secondary windings S, one in series with the lead' to the grid of each tube in the" Finch tripping and locking circuit 42. Theanodes and grids of the tubes in 42 are cross connected as shown by resistances so that a potential change on one grid produces through the tubes and circuits a positive tripping action. By means of pulses delivered to the Finch tripping and locking circuit the circuit is caused to turn on and off a tone keyer for the transmission of a keyed carrier telegraph, printer, or facsimile signal. The action of the tripping circuit and tone keyer is substantially identical with that described fo'r Figf ure 2. A difference resides in the use of multigrid vacuum tubes in the tone keyer of Figure 1,

`and the use of transformer coupling to the tripping circuit.

To explain'the action of the keyer system of Figure 2 in shortening (or lengthening-if desired) the signalling pulses it will be noted that the potential across the primary winding P of the `transformer 40 and therefore across the secondary windings S also, is dependent upon the potential across condenser Cs plus the potential drop in the parallel combination of the resistance R4 and the rectier 6.

When the potential across condenser C1 is reversed by the transmitter mechanism 2 the con.- denser YC3 tends to delay the rise of potential across the primary winding of the transformer.

.When the potential reverses to one potential polarity,- or direction, current flows easily through the rectifier and due to voltage Vdrop in resistance Ra considerably delays the application of potential to the transformer primary winding while the condenser is being charged through R3. en the potentialv reverses to the other potential polarity or direction, current can not flow in substantial amount through the rectier 6 there is little voltage drop in resistance Rs and nearly .full potential is applied almost instantly to the primary winding of the transformer. Thus, with equal time intervals of reversing potentials across condenser C1, there will 'exist unequal time intervals of reversing poten- -tials across 'the primary winding of the transformer. Therefore, the outputfrom the Finch tripping circuit 42 and from the tone signal keyer 30 will have an altered relation between on and olf time periods. Ifthe on -periods have been Vshortened and the off periods Alengthened, by a correct amount,-then signal elongation in transmission'may be overcome. d

.Practical experience indicates that, for ordinary purposes, a. ixed amount of time may be subtracted from each marking or on period and added to the spacing nor oi period. Preferably the time subtracted should just balance or even a little more than balance the signal elongation between transmitter and receiver terminal mechanisms. When the receiver mechanism is a recorder which writes a record of the message on a moving tape, inthe form of an undulating line drawn on the tape, the message is more readable if something has been subtracted from the marking time periods to compensate for the eiiect of the width of line drawn by the recorder. Therefore, my invention may be applied to compensate for the recorder characteristics as well as for intervening circuit characteristics.

Although I have described my invention as applied to the transmitter it will be evident that I may also apply it in radio receivers, especially in those systems where the receivers are used to key a carrier wave for transmission over a wire line to a central traffic oiiice. Such receiving systems have been used in the communications art for the past fifteen years or more and have been described by H. H. Beverage, H. O. Peterson, J. B. Moore and others. See Beverageet al. United States Patent #1,874,866 dated August 30, 1932 and Moore United States Patent #2,089,-

v568 dated August 10, 1937.

In practice, I may so design my system that any of the circuit elements used are variable either at the time of installation or during ordinary operatio-n. The degree of flexibility of lcircuit elements will in each case be governed by the requirements of the service, cost, reliability,

etc.

The rectiiier shown in the two figures may be any of the Well known types including vacuum tubes, gas or vapor glow discharge tubes, oxide rectifiers, etc. In practice cuprous oxide lm rectiiiers of the kind commonly used for small storage battery charger rectifers, small direct current power supplies, etc., are recommended. Such rectiers with any reasonable range of voltage, current carrying capacity, etc., are readily available commercially and can be recommended.

I- claim: v

1. A keying system including means for controlling the weight of keying comprising, means for producing positive and negative impulses characteristic of signals, a condenser and a resistance in series, means for impressing said impulsespn said condenser, a storing device, and uni-directional means connecting said resistance and vcondenser to said storing device, whereby energy from said condenser and resistance is stored up in said device at different rates by the positive and negative impulses respectively.

2. A keying system including means for controlling the weight of keying comprising, means for producing positive and negative impulses characteristic of signals, a condenser and a. resistance in series connected with said means to be energized by said impulse, a second condenser, and a rectier connecting said resistance and first condenser to said second condenser, whereby energy from said first resistance and first condenser is stored up in said second condenser at diiierent rates by said positive and negative impulses respectively. Y 3. A keying system including means for controlling the weight of keying comprising, means for producing positive and negative impulses characteristic of signals, a condenser and a resistance in series connected with said means, a rectier and a condenser in series, means connecting said series rectifier and condenser in shunt to said resistance and rst condenser, a resistance in shunt to said rectier, and a utilization circuit connected in shunt to s aid second condenser.

4. In a signalling system means for producing impulses the polarity of which relative to a fixed potential are characteristic of marking periods and spacing periods, means for keying-a transmitter of carrier waves in accordance with said impulses and means to compensate for elongation of carrier wave signals by multi-path transmission comprising means interposed between said rst and second means for automatically reducing the time length of marking periods and increasing the time length of spacing periods.

5. In a signalling system, means for producing impulses the polarity of which relating to a xed potential are characteristic of marking periods and spacing periods, means'for keying a transmitter of carrier Waves in accordance with said impulses and means to compensate for elongation of carrier wave signals by multi-path transmission comprising', an electrical circuit interposed between said rst and second means said electrical circuit being energized by said impulses, a condenser in said electrical circuit and a unilateral, conductive device in shunt to said condenser whereby said potentials of different polarity charge said condenser at different rates.

6. In a keying system to be used with radio telegraphy transmitter systems wherein signals are distortedl in length during transmission, an electrical circuit including, means for `applying ferent time constants of response in said elec,

trical circuits for said .potential or current changes of diierent polarity.

7. In a keying system to be used with radio telegraphy transmitter systems wherein signals are eiected by two path transmission, means for producing current pulses of polarity relative to a fixed polarity characteristic of signals and spaces, circuits having a different time constant of response for potential or current changes in one direction as compared with the time constant of response for potential or current changes in the opposite direction, means for applying saidpulses to said circuits, and means connected with said circuits for keying a telegraphy transmitter.

8. Ina telegraphy system means for producing potentials the value of which relative to a fixed potential arev characteristic of signals and spaces, a relay connected t0 said means to be excited by said potentials to produce current flow characteristic of said signals and spaces and means for adjusting the relative lengths of said signals and spaces comprising a current storing condenser in said connection to be charged by said potential and means in said connection for lowering the rate at which said condenser is charged by certain of said potentials.

CLARENCE W. HANSELL. 

